Sometimes, and I can always tell by the fact I get some pain by the person who is doing the blood test.
If I get pain when the needle is inserted I can usually reckon on having a bruise - no pain, no bruise.
Farley

I have tricky veins apparently, and usually get a great big bruise when blood is taken. My most recent one left no bruise at all though, so I wonder whether mt 'tricky' veins are actually caused by a 'not so good' nurse ...

usually no problem quick and easily done.
Depends on the nurse doing it some are hopeless, like the one i had the misfortune to attend a few weeks ago had to wait 2 hours, she tried one arm could not find the vein then tried the other arm,stuck the needle in an wriggled it around, no use then tried again about an inch away just a little blood and bruising, then said , she could not try again as they could only try twice, told me to come again the next day, still have not been back.

I've had some whoppers but I have a lovely lady now who does such a good job, I barely feel it and it doesn't bruise. (curse those regular blood tests.) Anaesthetic . . .different story . . . .I was once bruised from wrist to elbow. Horrifying.

Sometimes. I know sometimes it can depend upon the amount of experience of the nurse. However, I must also take some of the blame on some occasions. If I have to have a fasting blood test, it is often very hard to get a vein, so they have to ' hunt around ' for a suitable vein. Usually I don't get bruises unless they have been particularly rough, or if I am sick at the time, my blood vessel walls might be quite thin.